Group III-Nitride semiconductors have attracted great interest for their application in power electronics. Due to the high critical electric field (e.g., 3 MV/cm), high density (e.g., 1013/cm2) and the high mobility (e.g., >1200 cm2/V·s) two-dimensional-electron-gas (2DEG) arising in group III-nitride heterostructures, group III-nitride-based transistors have the potential to greatly reduce power loss and minimize system size relative to Si-based power electronic devices such as power switches.
A power switch has an on state that allows the device to conduct current, and an off state that prevents the device from conducting current. When in the on state, a power switch may conduct tens or hundreds of amperes while the voltage across the switch is less than one volt. When in the off state, the power switch typically must withstand hundreds or thousands of volts while conducting substantially zero current. The voltage that the device can withstand in the off state while conducting no more than a given small value of current is sometimes referred to as the breakdown voltage.
Electric field management is important in high voltage power switches. Currently, field-plate structures are widely used in III-Nitride power devices such as transistors and diodes to reduce the electric field concentration at the edge of the depletion region (e.g. the edge of the gate electrode in transistors or the anode in diodes) of the devices in their off-state and increase their breakdown voltages. However, the fabrication of conventional field-plate structures can become increasingly difficult as a larger number of field-plates may be required to reduce the electric field concentration when the device breakdown voltage increases. The additional field-plates also increase the overall capacitance of the device, reducing its switching frequency.